Methods, systems, and apparatuses for manufacturing rotational spun appliances

ABSTRACT

The present disclosure relates to methods and systems for manufacturing rotational spun materials. The rotational spun materials are medical appliances or other prostheses made of, constructed from, covered or coated with rotational spun materials, such as polytetrafluoroethylene (PTFE).

RELATED APPLICATION

This application claims priority to U.S. Provisional Application No.61/780,524 filed on Mar. 13, 2013, titled METHODS, SYSTEMS, ANDAPPARATUSES FOR MANUFACTURING ROTATIONAL SPUN APPLIANCES, the entirecontents of which are hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure relates generally to rotational spun materials.More specifically, the present disclosure relates to methods and systemsfor manufacturing rotational spun appliances. Even more specifically,the rotational spun appliances are medical appliances or otherprostheses made of, constructed from, covered or coated with rotationalspun materials, such as polytetrafluoroethylene (PTFE).

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments disclosed herein will become more fully apparent fromthe following description and appended claims, taken in conjunction withthe accompanying drawings. While various aspects of the embodiments arepresented in drawings, the drawings are not necessarily drawn to scaleunless specifically indicated. These drawings depict only typicalembodiments, which will be described with additional specificity anddetail through use of the accompanying drawings in which:

FIG. 1A is a perspective view of one embodiment of a rotational spinningapparatus.

FIG. 1B is a perspective view of a variation of the embodimentillustrated in FIG. 1A.

FIG. 2 is a perspective view of another embodiment of a rotationalspinning apparatus.

FIG. 3A is a perspective view of another embodiment of a rotationalspinning apparatus.

FIG. 3B is a perspective view of a variation of the embodimentillustrated in FIG. 3A.

FIG. 3C is a perspective view of another variation of the embodimentillustrated in FIG. 3A.

FIG. 4 is a side view of the embodiment illustrated in FIG. 2.

FIG. 5A a perspective view of another embodiment of a rotationalspinning apparatus.

FIG. 5B is a perspective view of the same embodiment where a hub of therotational spinning apparatus has been rolled outside of a housing ofthe rotational spinning apparatus and also illustrating one embodimentof a tool configured to remove mandrels from the hub.

FIG. 6A is a perspective view of the hub of FIGS. 5A and 5B.

FIG. 6B is the same perspective view as in FIG. 6A, but without a shellof the hub.

FIG. 7 further illustrates the tool of FIG. 6B and the mandrel of FIG.6B removed from the hub.

DETAILED DESCRIPTION

It will be readily understood that the components of the embodiments asgenerally described and illustrated in the Figures herein could bearranged and designed in a wide variety of different configurations.Thus, the following more detailed description of various embodiments, asrepresented in the Figures, is not intended to limit the scope of thedisclosure, but is merely representative of various embodiments.

Medical appliances may be deployed in various body lumens for a varietyof purposes. Stents may be deployed, for example, in the central venoussystem for a variety of therapeutic purposes including the treatment ofocclusions within the lumens of that system. The current disclosure maybe applicable to stents or other medical appliances designed for thecentral venous system, peripheral vascular stents, abdominal aorticaneurism stents, bronchial stents, esophageal stents, biliary stents,coronary stents, gastrointestinal stents, neuro stents, thoracic aorticendographs, or any other stent or stent graft. Further, the presentdisclosure may be equally applicable to other prosthesis such as stentgrafts or grafts.

For convenience, many of the specific examples included below referencestents and/or grafts. Notwithstanding any of the particular medicalappliances referenced in the examples or disclosure below, thedisclosure and examples may apply analogously to any tubular prosthesesor other tubular medical appliance.

As used herein, the term “stent” refers to a medical applianceconfigured for use within a bodily structure, such as within a bodylumen. A stent may comprise a scaffolding or support structure, such asa frame, and/or a covering. Thus, as used herein, “stent” refers to bothcovered and uncovered scaffolding structures.

The phrases “connected to,” “coupled to,” and “in communication with”refer to any form of interaction between two or more entities, includingmechanical, electrical, magnetic, electromagnetic, fluid, and thermalinteraction. Two components may be coupled to each other even thoughthey are not in direct contact with each other. For example, twocomponents may be coupled to each other through an intermediatecomponent.

The directional terms “proximal” and “distal” are used herein to referto opposite locations. For example, the proximal end of a mandrel isdefined as the end closest to the actuator rotating the mandrel. Thedistal end is the end opposite the proximal end, along the longitudinaldirection of the mandrel.

In embodiments where a stent or another appliance is composed of a metalwire structure coupled to one or more layers of a film or sheet-likecomponents, such as a polymer layer, the metal structure is referred toas the “scaffolding” or “frame,” and the polymer layer as the “covering”or “coating.” The terms “covering” or “coating” may refer to a singlelayer of polymer, multiple layers of the same polymer, or layerscomprising distinct polymers used in combination. Furthermore, as usedherein, the terms “covering” and “coating” refer only to a layer orlayers which are coupled to a portion of the scaffold; neither termrequires that the entire scaffold be “covered” or “coated.” In otherwords, medical appliances wherein a portion of the scaffold may becovered and a portion remains bare are within the scope of thisdisclosure. Finally, any disclosure recited in connection with coveringsor coatings may analogously be applied to medical devices comprising oneor more “covering” layers with no associated frame or other structure.

Medical device coverings may comprise multilayered constructs, comprisedof two or more layers which may be serially applied. Further,multilayered constructs may comprise nonhomogeneous layers, meaningadjacent layers have differing properties. Thus, as used herein, eachlayer of a multilayered construct may comprise a distinct layer, eitherdue to the distinct application of the layers or due to differingproperties between layers.

Additionally, as used herein, “tissue ingrowth” or “cellularpenetration” refers to any presence or penetration of a biological orbodily material into a component of a medical appliance. For example,the presence of body tissues (e.g., collagen, cells, and so on) withinan opening or a pore of a layer or component of a medical appliancecomprises tissue ingrowth into that component.

Further, as used herein, “attachment” of tissue to a component of amedical appliance refers to any bonding or adherence of a tissue to theappliance, including indirect bonds. For example, tissue of some kind(e.g., collagen) may become attached to a stent or graft covering(including attachment via tissue ingrowth) and another layer of biologicmaterial (such as endothelial cells) may, in turn, adhere to the firsttissue. In such instances, the second biologic material (endothelialcells in the example) and the tissue (collagen in the example) are“attached” to the stent or graft covering.

Furthermore, throughout the present disclosure, certain rotational spunmaterials may be referred to as inhibiting or promoting certainbiological responses. These relative terms are intended to reference thecharacteristics of rotational spun materials made utilizing thedisclosed methods, systems, and apparatuses as compared with respect toother materials or coatings.

Rotational spinning refers generally to processes involving theexpulsion of flowable material from one or more orifices, the materialforming fibers which are subsequently deposited on a mandrel. Examplesof flowable materials include dispersions, solutions, suspensions,liquids, molten or semi-molten material, and other fluid or semi-fluidmaterials. In some embodiments, the rotational spinning processes arecompleted in the presence or absence of an electric field.

One example of a rotational spinning process comprises loading a polymersolution or dispersion into a cup or spinneret configured with orificeson the outside circumference of the spinneret. The spinneret is thenrotated, causing (through a combination of centrifugal and hydrostaticforces, for example) the flowable material to be expelled from theorifices. The material may then form a “jet” or “stream” extending fromthe orifice, with drag forces tending to cause the stream of material toelongate into a small-diameter fiber. The fibers may then be depositedon a collection apparatus. Exemplary methods and systems for rotationalspinning can be found in U.S. Patent Publication No. US2009/0280325,titled “Methods and Apparatuses for Making Superfine Fibers,” thecontents of which are herein incorporated by reference in theirentirety.

The present disclosure relates to methods of making a rotational spunappliance. In some embodiments, the methods comprise rotating aspinneret around a first axis to produce spinning fibers. The methodsfurther comprise rotating a plurality of mandrels, each of the mandrelsrotating about its own axis, wherein each mandrel's own axis of rotationis not the same as the first axis of rotation. The methods furthercomprise contacting the spinning fibers with the rotating mandrels, suchthat fibers are deposited on the mandrels.

The methods may further comprise collectively and simultaneouslyrotating the plurality of mandrels around the first axis of rotation.

In some embodiments, each mandrel's own axis of rotation isperpendicular to the first axis of rotation. The rotation of eachmandrel around its own axis of rotation may result in the surface of themandrel turning in the same direction as the spinning fibers arespinning. The rotation of each mandrel around its own axis of rotationmay result in the surface of the mandrel turning in an oppositedirection as the spinning fibers are spinning.

In some embodiments, each mandrel's own axis of rotation is radiallytangential to the first axis of rotation.

In some embodiments, the rotation of the plurality of mandrels aroundthe first axis of rotation is in the same direction as the rotation ofthe spinneret. In other embodiments, the rotation of the plurality ofmandrels around the first axis of rotation is in the opposite directionas the rotation of the spinneret.

In some embodiments, the plurality of mandrels are removable from thefield of fibers produced by the spinneret during startup and shutdown ofrotation of the spinneret. In such embodiments, the rotation of each ofthe plurality of mandrels around its own axis and around the first axisis startable and stoppable while the plurality of mandrels are removedfrom the field of fibers produced by the spinneret.

In some embodiments, the methods further comprise placing fiber-wrappedmandrels in a sintering oven and sintering the fiber-wrapped mandrels.

Rotational spinning may be configured to create tubular structurescomprised of elongate fibers, including nanofibers (i.e., fibers whichare smaller than one micron in diameter) or microfibers (i.e., fiberswhich are between one micron and one millimeter in diameter). In someinstances the fibers are randomly disposed, while in other embodimentsthe alignment or orientation of the fibers is somewhat controlled orfollows a general trend or pattern. Regardless of any pattern or degreeof fiber alignment, as the fibers are deposited on a mandrel or onpreviously deposited fibers, the fibers are not woven, but rather areserially deposited on the mandrel or other fibers. Because rotationalspinning may be configured to create a variety of structures, as usedherein, the term “non-woven material” is intended to be broadlyconstrued as referring to any rotational spun structure.

FIG. 1A illustrates a rotational spinning apparatus 101. The illustratedapparatus 101 comprises a spinneret 110 disposed near the center of agenerally circular surface, such as disk 115. In the illustratedembodiment, disk 115 forms a ring around spinneret 110. Spinneret 110further comprises orifices 117 located around the circumference ofspinneret 110 and an internal reservoir. The illustrated apparatus 101further comprises actuators 120 mounted on the upper surface of disk115. Mandrels 125 extend from actuators 120 toward the radial center ofdisk 115. A support member rotatably engages the ends of mandrels 125and supports each of mandrels 125.

Spinneret 110 is configured to rotate around a first axis of rotation106. The internal reservoir is configured to be filled with a flowablematerial. In some instances polymer dispersions, including aqueousdispersions or polymer solutions, are used as the flowable material.Spinneret 110 is configured to be rotated such that the flowablematerial is forced out of the orifices 117. Molecules, including polymerchains, may tend to disentangle and/or align as the material is forcedthrough the orifice 117. Additionally, in some embodiments the orifice117 comprises a needle or nozzle that extends from the outsidecircumference of spinneret 110. Still further, in some embodiments theorifice 117 may comprise a cannula configured with a quick connection,such as a luer connection, allowing for rapid exchange of variouscannula sizes. Any spinneret known in the art may be used, such as thosedisclosed in U.S. Patent Publication No. US2009/0280325 referencedabove.

In some embodiments, spinneret 110 is configured to be rotated at about500 rotations per minute (RPM) to about 25,000 RPM. It is known in theart what rotational speeds may be used to develop a particular fiberfrom a particular flowable material. Any spinneret rotational speedcompatible with a desired fiber may be used. The fibers may loopcompletely around spinneret 110 one or more times before contactingmandrels 125.

Disk 115 is configured to rotate separately from spinneret 110 butaround the same first axis of rotation 106. Disk 115 may be configuredfor selectively rotating in the same direction or the opposite directionas spinneret 110. In FIG. 1A, both spinneret 110 and disk 115 areillustrated as rotating counter-clockwise around first axis of rotation106. In some embodiments, disk 115 is selectively configured forrotating at a slower speed than spinneret 110. Disk 115 may beconfigured for rotating at speeds of 1 to 1,000 RPM. In someembodiments, disk 115 may be configured for rotating at speeds of 1 to900 RPM, 1 to 800 RPM, 1 to 700 RPM, 1 to 600 RPM, and 1 to 500 RPM. Thediameter of disk 115 may be determined by the length of mandrels 125,which in turn may be determined by the desired length of medicalappliances made upon mandrels 125.

Disk 115 comprises an opening 140 configured to allow access forspinneret 110. Disk 115 may be lifted away from spinneret 110 as disk115 is separated from apparatus 101 for placement in a sintering oven.Alternatively, mandrels 125 may be separable from disk 115 and placed inthe sintering oven without disk 115.

Actuators 120 are mounted on disk 115 and configured to rotate mandrels125. Actuators 120 are configured to rotate with disk 115 as it rotatesrelative to spinneret 110. Each actuator 120 may comprise an electricmotor, such as, for example, a direct-current stepper motor, forrotating a mandrel 125. The motor may be configured to handle sinteringtemperatures for when disk 115 is removed from rotational spinningapparatus 101 and placed in a sintering oven. Any method of transferringpower to any electric motors of actuators 120 may be used. For example,the electric motors may be battery powered or wirelessly powered. Inanother example, the electric motors may be powered by rotatingelectrical contacts mounted beneath disk 115 that maintain communicationwith stationary electrical contacts while disk 115 rotates.

Alternatively, each actuator 120 may comprise a gear drive for rotatinga mandrel 125. Each gear drive may be configured to handle sinteringtemperatures for when disk 115 is removed from rotational spinningapparatus 101 and placed in a sintering oven. Each gear drive maycomprise a right angle gear drive for operably coupling the shaft ofmandrel 125 to a power source. Each gear drive of an actuator 120 mayhave its own power source, such as an electric motor mounted beneathdisk 115. In that embodiment, the electric motors may be configured in aring beneath disk 115. The ring may be configured to rotate with disk115. The ring may further be configured to be separable from disk 115prior to disk 115 being placed in a sintering oven so that the motorsare not placed in the sintering oven. Similar to the electric motorsdiscussed previously, any method of transferring power to the electricmotors may be used. For example, the electric motors may be batterypowered, wirelessly powered, or powered by rotating electrical contactsthat maintain communication with stationary electrical contacts whiledisk 115 rotates.

In another variation of the gear drive embodiment, all or multiple geardrives of the actuators 120 may be operably connected to a single powersource. For example, a single electric motor may be mounted beneath disk115. The motor may be operably connected to each of the actuators 120,such as via a belt and pulley system. The motor and/or the belt andpulley system may be separable from disk 115 prior to disk 115 beingplaced in a sintering oven.

Mandrels 125 are operably connected to actuators 120 and configured forrotation by actuators 120. Mandrels 125 may be selectively rotated in aforward or reverse direction around its own axis of rotation 126. InFIG. 1A, mandrels 125 are illustrated as rotating in the forwarddirection relative to actuators 120. In the illustrated embodiment,rotation of mandrels 125 in the forward direction results in the surfaceof mandrels 125 turning in the same direction as the spinning fibers arerotating. In other embodiments, mandrels 125 are rotated in the reversedirection of that illustrated. The reverse direction would result in thesurface of mandrels 125 turning in the opposite direction from thedirection the spinning fibers are rotating.

In some instances, mandrels 125 rotate at rates between about 1 RPM andabout 3,000 RPM, including rates from about 100 RPM to about 2,000 RPM,including about 1,500 RPM, or about 50 RPM to about 300 RPM, includingabout 150 RPM. In some instances, the rotational speed of one or more ofmandrels 125 is related to the rate at which spinneret 110 producesfibers. For example, in some embodiments, faster mandrel 125 rotationalspeed may be correlated with higher total fiber production rates forspinneret 110. In some embodiments, all of mandrels 125 turn at aboutthe same speed. In other embodiments, some or all of mandrels 125 turnat different speeds.

FIG. 1A illustrates mandrels 125 as essentially cylindrical in shape. Itshould be understood that the diameter of mandrels 125 may be selectedbased on the desired inner diameter of a medical appliance.Additionally, mandrels 125 may have a shape other than cylindrical. Forexample, mandrels 125 may have a concave or convex shape, such that theends of the resulting medical appliance, such as a stent or graft, haveends that are either wider or narrower than the middle of the appliance.

The surface of mandrels 125 is illustrated as smooth. The surface ofmandrels 125 may have any texture or surface profile desired. Forexample, mandrels 125 may have corrugated ridges and grooves that wraparound the surface of mandrels 125. The ridges and grooves may impartadditional structural strength in a medical appliance made with mandrels125.

Furthermore, in some embodiments, one or more of mandrels 125 may beconfigured for use in connection with a vacuum system. For example,openings in the surface of mandrels 125, such as micropores, may tend todraw fibers toward mandrels 125 in instances where the interior ofmandrels 125 has lower pressure than the exterior of mandrels 125.Likewise, in some embodiments, one or more of mandrels 125 may have anelectrostatic charge suitable for attracting fibers to mandrels 125.

Apparatus 101 is illustrated as having twenty mandrels 125. Apparatus101 may have any number of mandrels depending upon factors such as thedesired space between mandrels 125, radius of disk 115, and/or desiredlength, shape, and width of mandrels 125. In FIG. 1A, each mandrel's 125own axis of rotation 126 is parallel to the upper surface of disk 115.In FIG. 1A, each mandrel's 125 own axis of rotation 126 is alsoperpendicular to first axis of rotation 106, such that the longitudinalaxis of each of mandrels 125 extends radially from opening 140 of disk115. Therefore, each mandrel's 125 own axis of rotation 126 is radiallydifferent from each other.

In a variation of the illustrated embodiment of FIG. 1A, mandrels 125may not be oriented parallel to the upper surface of disk 115. Forexample, mandrels 125 may be oriented perpendicular to the upper surfaceof disk 115. In that example, mandrels 125 would be vertically orientedand each mandrel's own axis of rotation 126 would be parallel to firstaxis of rotation 106. Additionally, combinations of mandrels 125 in avariety of orientations may be used simultaneously on a single disk 115.

Support member is configured to support the distal ends of mandrels 125.FIG. 1A illustrates support member as a cylindrical hub protrudingupward from the upper surface of disk 115. In FIG. 1A, spinneret 110extends through the hollow center of support member. Support member maycomprise any number of structures and/or shapes for supporting thedistal ends of mandrels 125. For example, instead of a cylindrical hub,support member may comprise separate posts extending upward from theupper surface of disk 115. Each post may support the distal end of asingle mandrel 125 and allow rotation of that mandrel 125.

The apparatus 101 may be utilized to create tubular structures ofrotational spun fibers deposited on mandrels 125. As the dispersion isexpelled from the internal reservoir of spinneret 110, drag or otheraerodynamic forces acting on the stream or jet of material may cause thestream of dispersion to elongate and bend, forming a relativelysmall-diameter fiber of material. In some instances drag may be a shearforce with respect to the stream. Additionally, certain components ofthe dispersion, such as the dispersion medium or solvent, may partiallyor fully evaporate as the material is drawn into fibers. In embodimentsutilizing flowable materials which have no solvent, such as moltenmaterial, there may be no evaporation as the material is drawn intofibers.

The fibers eventually contact, and are deposited on, mandrels 125. Thecombination of forces described above may interact as the fibers aredeposited, causing the fibers to be disposed in random patterns at auniform thickness across the surface of mandrels 125, particularly whenmandrels 125 are oriented horizontally as illustrated in FIG. 1A.

FIG. 1B illustrates a variation of disk 115 that further comprises vents150 that perforate disk 115. In this embodiment, air may be blownthrough vents 150 to introduce air currents that partially control thedeposition of the fibers on mandrels 125. Vents 150 are illustrated as aradial array of pinholes in disk 115. There may be any number of vents150 arrayed in any pattern. Additionally, other structures and devicesfor introducing air currents to the fibers may be used. For example,vents 150 may be flaps angled upward from the surface of disk 115,instead of air holes. The flaps may be configured so that as disk 115rotates at a desired speed the desired air currents are generated.

FIG. 1B also illustrates a variation of disk 115 that further comprisesshields 160. Shields 160 are configured to prevent rotating fibers fromspinning beyond the perimeter of disk 115 and to prevent rotating fibersfrom becoming so long that the ends of fibers become entangled with eachother and deposit on mandrels 125 as tangled clumps. Shields 160 areillustrated as flat rectangular pillars extending upward from the uppersurface of disk 115. Shields 160 are also illustrated as located aroundthe perimeter of disk 115. Shields 160 can align with vents 150. Aircurrents may be deflected along the inner surface of shields 160 andtend to deflect fibers from contacting shields 160.

Shields 160 may be of any shape compatible with preventing rotatingfibers from spinning beyond the perimeter of disk 115. There may be anynumber of shields 160 in any pattern. For example, shields 160 may be asingle continuous sheet or mesh that wraps around the perimeter of disk115. Additionally, shields 160 may be configured to introduce aircurrents that direct rotating fibers toward mandrels 125. For example,shields 160 may be airfoils instead of pillars. The airfoils may bepropeller-shaped and configured to generate air currents as disk 115rotates, such that rotating fibers are pushed radially inward by the aircurrents toward mandrels 125.

FIGS. 2-7 illustrate apparatuses analogous to that shown in FIGS. 1A and1B. It will be appreciated by one of skill in the art having the benefitof this disclosure that analogous components of the apparatuses may beinterchangeable and that disclosure provided in connection with eachembodiment may be applicable to the other and vice versa.

FIG. 2 is a perspective view of a rotational spinning apparatus 201.Rotational spinning apparatus 201 includes a spinneret 210 comprising aninternal reservoir and orifices 217. As compared to apparatus 101 ofFIG. 1A, in the embodiment of FIG. 2 support member is not present andinstead mandrels 225 are cantilevered from actuators 220. Disk 215comprises opening 240 configured to allow access for spinneret 210.

FIGS. 3A and 3B are perspective views of a rotational spinning apparatus301. Rotational spinning apparatus 301 includes a spinneret 310comprising an internal reservoir and orifices 317. Similar to apparatus201 of FIG. 2, the support member of apparatus 301 is not present andmandrels 325 are cantilevered from actuators 320.

In the illustrated embodiment of FIGS. 3A and 3B, only four mandrels 325are present. More or less mandrels 325 may be present. In both FIGS. 3Aand 3B, each mandrel's 325 own axis of rotation 326 is parallel to theupper surface of a disk 315. In FIG. 3A, each mandrel's 325 own axis ofrotation 326 is perpendicular to a first axis of rotation 306. Or statedanother way, the longitudinal axis of each of mandrels 325 extendsradially from an opening 340 of disk 315. Each mandrel's 325 own axis ofrotation 326 is radially different from each other. In FIG. 3B, eachmandrel's 325 own axis of rotation 326 is radially tangential to firstaxis of rotation 306. Or stated another way, the longitudinal axis ofeach of mandrels 325 is oriented perpendicular to opening 340 in thecenter of disk 315.

In the illustrated embodiment of FIGS. 3A and 3B, actuators 320 may beconfigured to be pivotable to allow mandrels 325 to either extendradially from opening 340 in the center of disk 315 or to be orientedperpendicular to opening 340 in the center of disk 315. In othervariations, actuators 320 may not be pivotable and instead disk 315 mayhave alternative mounting holes and actuators 320 may be mounted invarious orientations.

In a variation of the embodiment illustrated in FIGS. 3B and 3C,mandrels 325 may be permanently oriented perpendicular to opening 340 atthe center of disk 315. In another variation, mandrels 325 may beoriented at any angle relative to opening 340 at the center of disk 315.When mandrels 325 do not extend radially from opening 340 of disk 315(i.e., each mandrel's 325 own axis of rotation 326 is not perpendicularto first axis of rotation 306, such as illustrated in FIG. 3B), then itmay be possible to increase the length of mandrels 325 over thatillustrated in FIGS. 3B and 3C.

In another variation of the embodiment illustrated in FIG. 3B, insteadof mandrels 325 being cantilevered by actuators 320, the distal ends ofmandrels 325 may be supported by individual supports, analogous tosupport member of apparatus 101.

FIG. 3C illustrates an embodiment similar to that illustrated in FIG.1B, namely vents 350 and shields 360 are illustrated in FIG. 3C.

FIG. 4 illustrates a side view of apparatus 201 and illustrates oneembodiment of a power source that may be used for rotating disk 215.FIG. 4 illustrates a belt drive system attached to the underside of disk215. A drive 216 is attached to the underside of disk 215. Drive 216 isoperably connected by a belt 218 to a power source 219. In theillustrated embodiment, power source 219 is an electric motor. Methodsof rotating disks are known in the art. Any number of power sources anddrive systems may be used to rotate disk 215. It should be understoodthat the discussion of FIG. 4 applies to any of the disclosedapparatuses, including apparatuses 101 and 301.

Apparatuses 201 (and also apparatuses 101 and 301 by analogy) mayfurther be configured with a moveable slide configured to allow disk215, drive 216, belt 218, and power source 219 to be slid away fromspinneret 210. In such embodiments, spinneret 210 may not extend throughopening 240. Instead spinneret 210 may be suspended above disk 215. Insuch embodiments, when disk 215 is in operational position, orifices 217would still occupy the same geographical space relative to disk 215 asthey do in FIG. 2. The moveable slide allows disk 215 and/or mandrels225 to either start up or slow down rotation while separated fromspinneret 210 and then be placed in the operating position when atoperational speed. Likewise, spinneret 210 is able to reach operationalspeed and optimal fiber production before mandrels 225 are exposed tothe produced fibers. Similarly, spinneret 210 would be able to ceasefiber production without exposing mandrels 225 to suboptimal fibers.

FIG. 5A illustrates a rotational spinning apparatus 401. Apparatus 401comprises a hub 415 configured to rotate around a first axis of rotation406. Apparatus 401 further comprises mandrels 425 operably connected tohub 415 and each configured for rotation by hub 415 around its own axisof rotation 426 that is not the same as first axis of rotation 406, suchthat during operation of apparatus 401, mandrels 425 are rotated aroundboth first axis of rotation 406 and each mandrel's 425 own axis ofrotation 426.

Apparatus 401 further comprises a spinneret 410 separate from hub 415and configured to also rotate around first axis of rotation 406.Spinneret 410 includes orifices 417. Spinneret 410 may be operablycoupled to an actuator (not shown) configured to rotate spinneret 410above hub 415.

A difference between apparatus 401 and apparatuses 101, 201, and 301 isthat the mandrels extend from a hub instead of being mounted on a disk.Additionally, the actuators for the mandrels are built into hub 415 inapparatus 401. It should be understood that analogous disclosureregarding apparatuses 101, 201, and 301 applies also to apparatus 401and vice versa.

In the illustrated embodiment, hub 415 has eight mandrels 425 extendingoutwardly from it. Hub 415 may have any number of mandrels 425 extendingoutwardly from it. Likewise, hub 415 may have any structure compatiblewith rotating mandrels 425 around first axis of rotation 406 and alsorotating each of mandrels 425 around its own axis of rotation 426.

In the illustrated embodiment apparatus 401 further comprises a housing480 configured to allow hub 415 to be rolled inside housing 480 duringoperation of apparatus 401 and configured to allow hub 415 to be rolledoutside housing 480 when apparatus 401 is not in operation. Rolling hub415 outside of housing 480 may make it easier to remove mandrels 425from hub 415. In the illustrated embodiment, spinneret 410 is mountedand located in an upper portion of housing 480 such that spinneret 410is located above hub 415 when hub 415 is rolled inside housing 480. FIG.5A illustrates hub 415 rolled inside housing 480. FIG. 5B illustrateshub 415 rolled outside housing 480. Housing 480 is illustrated assupporting hub 415 via support rods 418. It should be understood anysupport structures compatible with the functions of hub 415 may be used.

Housing 480 may further comprise a retractable cover configured forinsertion between spinneret 410 and hub 415. The retractable cover wouldbe inserted between spinneret 410 and hub 415 during startup andshutdown of apparatus 401. While the retractable cover is in placespinneret 410, hub 415, and/or each mandrel 425 may be either brought upto operational speed or shutdown. The retractable cover would then beremoved when spinneret 410, hub 415, and mandrels 425 are at operationalspeed. In this way, fibers produced by spinneret 410 at less thanoptimal speeds would not be deposited on mandrels 425.

FIG. 6A illustrates hub 415 with a shell 416 in place and with spinneret410 oriented above hub 415. It should be understood that none of thesupporting structures for hub 415 or spinneret 410 are shown in thisFigure. FIG. 6B illustrates hub 415 without shell 416. Shell 416 may beconfigured in any manner compatible with keeping fibers out of actuatingcomponents of hub 415. In apparatus 401, mandrels 425 extendhorizontally outward from hub 415 so that each mandrel's 425 own axis ofrotation 426 lies in a plane that is perpendicular to the line of firstaxis of rotation 406. In apparatus 401, some of the mandrel's own axesof rotation 426 are the same as each other, but different from firstaxis of rotation 406. In apparatus 401, each mandrel 425 has acorresponding opposite mandrel 425 that extends outwardly from hub 415in the opposite direction. In apparatus 401, each mandrel 425 and itscorresponding opposite mandrel 425 each have the same own axis ofrotation 426.

In the illustrated embodiment, the gears that actuate mandrels 425 aresynchronized together so that each mandrel 425 turns at the same speed.Hub 415 may be configured such that different mandrels 425 turn atdifferent speeds. Hub 415 may include actuators configured to rotatemandrels 425 and actuators configured to rotate hub 415. For example, astationary actuator may be operably coupled underneath hub 415 andconfigured to rotate hub 415. Additionally, a rotatable actuator may becoupled to hub 415 and configured to rotate with hub 415 and rotatemandrels 425 at the same time.

FIG. 7 illustrates mandrel 425 separated from hub 415. In FIG. 7,mandrel 425 is illustrated with a cog 450 attached to the proximal endof mandrel 425. It should be understood that cog 450 may be retained inhub 415 and mandrel 425 removed from cog 450. FIGS. 5B and 7 illustratea tool 460. Tool 460 is not a part of apparatus 401, but may be usedwith apparatus 401 to remove mandrels 425 from hub 415. The distal endsof mandrels 425 may be configured to mate with tool 460. Tool 460 may beconfigured such that an individual using tool 460 may able to removemandrels 425 from hub 415 using only tool 460. This may prevent damageto unsintered fibers deposited on mandrels 425.

Mandrels 425 may be configured for removal from hub 415 using a quickconnect coupling. As used herein, a “quick connect coupling” is anydevice, connector or attachment mechanism that allows removal ofmandrels 425 in less than 10 seconds. For example, FIG. 7 illustratesone embodiment of a quick connect coupling. Cog 450 includes a socketconfigured to receive the proximal end of a mandrel 425. The socket ofcog 450 includes a J-shaped slot in the sidewall of the socket. Mandrel425, in this illustrated embodiment, includes a peg protruding from theside of the proximal end of the mandrel 425. The peg is sized andconfigured to slide within the J-shaped slot of the sidewall of thesocket. During insertion of a mandrel 425 into the socket of cog 450,the peg is lined up with the long side of the J-shaped slot. Next,mandrel 425 is pushed into the socket, rotated, and then slightly pulledback until the peg has completely travelled the length of the J-shapedslot. Mandrel 425 is now ready for rotation by hub 415. Removal of amandrel 425 from the socket of a cog 450 follows a reverse process.Likewise, for removal of cog 450, such as for cleaning or maintenance,with the peg of a mandrel 425 fully engaged with the J-shaped slot,mandrel 425 can be twisted and pulled for disengagement of cog 450 fromhub 415 and pushed and twisted for reengagement of cog 450.

Regarding mandrels 125, 225, 325, and 425, one benefit of rotating theplurality of mandrels around the same first axis of rotation as thespinneret is that rotational speed may be optimized. For example, theoptimal speed for producing a fiber, such as a PTFE fiber, of aparticular diameter and length may be about 7,500 RPM. The optimal speedat which the fibers contact the mandrels may be about 6,500 RPM. Underthat scenario, the disk or hub may be rotated at about 1,000 RPM in thesame direction as the rotation of the spinneret so that the net speeddifference between the rotating fibers and the mandrels around the firstaxis of rotation is about 6,500 RPM. Of course, the orientation of eachmandrel's own axis of rotation, and rotational direction and speed ofrotation of the mandrels around each mandrel's own axis of rotation mayalso be optimized.

Regarding mandrels 125, 225, 325, and 425, the spinning motion of eachmandrel may tend to deposit the fibers around the entire surface of themandrel. Thus, as the fibers are deposited on each mandrel, a seamlesstube of fiber material may form on each mandrel. The density of thefibers, the thickness of the tube of material, and other characteristicsmay be controlled by such variables as the distance from the spinneretto the mandrels, the rotational speed and direction of the spinneret,the rotational speed and direction of the disk around the first axis ofrotation, the rotational speed and direction of each of the mandrelsaround its own axis of rotation, the number and orientation of themandrels, the characteristics of the flowable material being spun, andso forth. In some instances, the rotational spun material formed on amandrel may thus comprise a tubular membrane having no seam andsubstantially isotropic properties.

Furthermore, controlling the rotational speed of the disk and themandrels may influence both the density of the material formed on themandrels and the general alignment of fibers in the material. Forinstance, in some embodiments utilizing vertical mandrels (i.e., amandrel's own axis of rotation is parallel to the first axis ofrotation), the faster the mandrel is spinning the more the fibers maytend to be deposited in-line with other fibers. Further, the relativedensity of the fibers, for example, as measured by percent porosity, maybe controlled in part by the rotational speed of the mandrels.

Likewise, the orientation of the mandrels may influence the generalalignment of fibers in the material. For example, when the mandrels areoriented parallel to the upper surface of the disk with each mandrel'sown axis of rotation perpendicular to the first axis of rotation, suchas illustrated in FIGS. 1A, 1B, 2, 3A, 3C, and 4, then fibers may crosseach other at various and random points on the mandrels. This may havethe benefit of the resulting tubular structure having isotropicproperties, meaning the tubular structure has the same properties in alldirections.

The distance between the spinneret and the mandrels may impact thediameter of the fibers. In some embodiments, the longer the fibers aredrawn out before contacting the mandrels, the smaller the resultingfiber diameters. Similarly, smaller distances may be configured toproduce larger diameter fibers. Thus, the spinneret to mandrel distancemay be varied to achieve either microfibers or nanofibers.

Additional variables that may be controlled to affect the properties ofa rotational spun tubular structure include the viscosity of thesolution, dispersion, or other flowable material; the temperature of thespinneret; introduced air currents; and the thickness of the tubularstructure. In the case of fibers spun from molten material, the meltflow index (MFI) of the material may also impact the nature of the spuntubular structure. In some embodiments, materials with an MFI of fromabout 1 g/10 min to about 5,000 g/10 min, including from about 200 g/10min to about 1,500 g/10 min and from about 10 g/10 min to about 30 g/10min, will tend to form fibers when spun.

As discussed previously, in some embodiments it may be desirable tosinter the fibers after they are deposited on the mandrels. Whethersintering is desirable may depend on the particular flowable materialused to make the fibers. For example, sintering may be applicable toPTFE fibers, including PTFE fibers spun from a dispersion. The sinteringprocess may set or bond the structure of the fibers and remove anyremaining water or other dispersion medium or solvent.

In some embodiments, the fibers may be treated at a first temperature toremove solvents and a second temperature to sinter the fibers. Forexample, a PTFE tubular structure spun from an aqueous dispersion may befirst treated at a temperature below the sintering temperature of PTFEin order to remove any remaining water. For example, the tubularstructure may be heated to about 200 degrees C. to remove any remainingwater in the tubular structure. Further, other materials such assolvents or fiberizing agents may be evaporated or otherwise driven offat this stage. In some embodiments—as further detailed below—a PTFEdispersion may be mixed with polyethylene oxide (PEO) prior torotational spinning of the tubular structure. As also discussed in theexamples below, concentrations of PEO to 60 wt % PTFE dispersion fromabout 0.04 g/ml to about 0.12 g/ml, including from about 0.06 g/ml toabout 0.08 g/ml, may be used in some embodiments. In some instances,very high or very low concentrations of PEO may lead to shrinkage duringsintering or sputtering during rotational spinning of the material.

Treating the spun tubular structure at temperatures such as 200 degreesC. may force off remaining PEO as well as water. In some embodiments thePTFE tubular structure may then be sintered at about 385 degrees C. Inother embodiments, PTFE sintering may be completed at temperatures fromabout 360 degrees C. to about 400 degrees C., and/or at temperatures inexcess of the crystalline melt point of the PTFE (about 342 degrees C.).In other instances the tubular structure may only be heated to thesintering temperature, removing the remaining water and/or PEO whilesimultaneously sintering the PTFE. Additionally or alternatively, insome embodiments solvents or other materials may be removed by rinsingthe tubular structure.

Sintering may set the structure of the tubular structure even if thetemperature at which the material is sintered is not sufficient to causecross linking of the polymer chains. PTFE sintering may create solid,void-free PTFE fibers.

Processes such as the exemplary process described above may be utilizedto create structures comprised of small-diameter fibers, includingnanofibers. The fiber tubular structure may then be incorporated into amedical appliance configured for implantation in the human body. Somesuch structures, including nanofiber structures, may be configured topermit tissue ingrowth and/or endothelial growth or attachment on thetubular structure. For example, the tubular structure may be configuredwith openings within the fibers or similar structures configured topermit interaction with tissue and/or cells. As further detailed below,the percent porosity of a fiber tubular structure, the thickness of thetubular structure, and the diameter of the fibers comprising the tubularstructure may each be configured to create a fiber tubular structurewith desired properties, including a tubular structure that tends topermit or resist tissue ingrowth and/or endothelial growth orattachment.

In other embodiments a rotational spun tubular structure may beconfigured to resist tissue ingrowth into or through the tubularstructure. In such embodiments, the tubular structure may be configuredwith very small pores, or effectively no pores at all, thus preventingtissue ingrowth into or through the tubular structure. Certain medicalappliances may be constructed partially of rotational spun materialsconfigured to permit tissue ingrowth and/or endothelial growth orattachment and partially of rotational spun materials configured toresist tissue ingrowth and/or attachment. Characteristics of therotational spun fiber tubular structure, such as porosity and averagepore size, may be controlled during the rotational spinning process tocreate certain tubular structures which permit tissue ingrowth and/orendothelial growth or attachment and other tubular structures whichresist or are impermeable to tissue ingrowth and/or attachment.

In some embodiments, a PTFE dispersion may be used to rotationally spina tubular structure comprised of PTFE nanofibers. Furthermore, in someexemplary embodiments PEO may be added to the PTFE dispersion prior torotational spinning of the material. The PEO may be added as afiberizing agent, to aid in the formation of PTFE fibers within thedispersion or during the process of rotational spinning of the material.In some instances the PEO may more readily dissolve in the PTFEdispersion if the PEO is first mixed with water. In some examples thisincreased solubility may reduce the time needed to dissolve PEO in aPTFE dispersion from as long as multiple days to as little as 30minutes. After the material is rotational spun onto a mandrel, thematerial may then be sintered as further described below. In someinstances the sintering process will tend to set or harden the structureof the PTFE. Furthermore, as described above, sintering may alsoeliminate the water and PEO, resulting in a tubular structure ofsubstantially pure PTFE. Additionally, as also described above, thetubular structure may first be heat treated at a temperature below thesintering temperature of the PTFE, in order to remove water and/or PEOfrom the tubular structure. In some embodiments this step may becompleted at about 200 degrees C.

The water, PEO, and PTFE amounts may be controlled to optimize theviscosity, PEO/PTFE ratio, or other properties of the mixture. In someinstances adding water to the PEO before mixing with the PTFE dispersionmay aid in reducing the number of solid chunks in the mixture, lower thepreparation time for the mixtures, and reduce the time needed for thecombined mixture to solubilize.

A variety of materials may be rotational spun to form structures for usein medical appliances. Exemplary materials which may be rotational spunfor use in implantable appliances include PTFE, fluorinated ethylenepropylene (FEP), Dacron or Polyethylene terephthalate (PET),polyurethanes, polycarbonate polyurethanes, polypropylene, Pebax,polyethylene, biological polymers (such as collagen, fibrin, andelastin), and ceramics.

Furthermore, additives or active agents may be integrated with therotational spun materials, including instances where the additives aredirectly rotational spun with other materials. Such additives mayinclude radiopaque materials such as bismuth oxide, antimicrobial agentssuch as silver sulfadiazine, antiseptics such as chlorhexidine or silverand anticoagulants such as heparin. Organic additives or components mayinclude fibrin and/or collagen. In some embodiments, a layer of drugs orother additives may be added to a rotational spun appliance duringmanufacture. Additionally, some appliances may be constructed with acombination of synthetic components, organic components, and/or activeingredients including drugs, including embodiments wherein an applianceis comprised of alternating layers of these materials. Moreover, in someembodiments a medical appliance may consist of layers of rotational spunmaterials configured to control the release of a drug or another activelayer disposed between such layers. Active layers or ingredients such asdrugs or other active agents may be configured to reduce or otherwisemodify or influence the biological response of the body to theimplantation of the medical appliance.

Additionally, in some embodiments the material supplied to the internalreservoir of the spinneret may be continuously supplied (for example bya feed line), including embodiments where the reservoir is pressurizedor supplied by a pressurized source. Further, in some embodiments thematerial may be heated near or above its melting point prior torotational spinning, including embodiments wherein the material ismelted and not dispersed in a solvent. Thus, in some embodiments,rotational spinning molten material does not include the use ofsolvents; therefore there is no need to remove solvents from the tubularstructure at a later step in the process. In some instances the materialmay be supplied to the reservoir as pellets which are heated and meltedwithin the reservoir.

Additionally, in some embodiments rotational spun structures may becombined with electrospun structures, including embodiments where somelayers of material are rotational spun and some electrospun, but bothdeposited on the same mandrel. Electrospinning, and its use inconnection with medical appliances, is described in U.S. patentapplication Ser. No. 13/360,444, filed on Jan. 27, 2012 and titled“Electrospun PTFE Coated Stent and Method of Use,” which is herebyincorporated by reference in its entirety.

In some embodiments, rotational spun tubular medical devices, such asstents or grafts, may comprise one or multiple bifurcations or branches.Thus, medical devices which comprise a single lumen which splits orbifurcates into two or more lumens are within the scope of thisdisclosure. Likewise, medical appliances comprising a main lumen withone or multiple branch lumens extending from the wall of the main lumenare within the scope of this disclosure. For example, a thoracicstent—configured for deployment within the aorta—may comprise a mainlumen configured to be disposed in the aorta and branch lumensconfigured to extend into side branch vessels originating at the aorta.Similarly, in some embodiments such tubular medical devices mayalternatively be configured with access holes in the main lumenconfigured to allow access (possibly for additional stent or graftsplacement) and flow from the main vessel to any branch vessels extendingtherefrom.

In some embodiments, a branched medical appliance may be manufactured byfirst creating a branched mandrel similar in shape to the desiredbranched medical appliance. The entire mandrel may then be rotatedaround the axis of the main lumen portion and rotational spun fiberscollected over the entire surface of the mandrel. Any unwanted fibersbetween branches and/or the main lumen may be wiped off. The entiremandrel, with or without the actuator and disk, may then be placed in anoven and sintered. The appliance may then be removed from the mandreland placed on or within a frame structure, such as a stent frame. A dipor film coating (such as of FEP or PTFE) may then be applied over theconstruct to create an impervious outside layer and/or to further bondthe frame to the spun portion of the appliance.

In some embodiments, a branched medical appliance may be manufactured byfirst creating a branched mandrel in which the branched portions areremovable from the portion of the mandrel coinciding with the mainlumen. The leg or branch portions of the mandrel may be splayed 180degrees apart with a common axis of rotation. Thus, in some embodiments,the entire mandrel may form a T-shape. The entire mandrel may then berotated around the axis of the leg portions and rotational spun fiberscollected on the leg portions of the mandrel. The mandrel may then beoriented to rotate around the axis of the main lumen portion of themandrel, and any unwanted fibers disposed while spinning on thebifurcated leg portions may be wiped off. The mandrel may then berotated around the axis of the main lumen portion and fibers collectedon the main lumen portion of the mandrel. The entire mandrel, with orwithout the actuators and disk, may then be placed in an oven andsintered. The mandrel portions associated with the bifurcated legs maythen be removed from the leg or branch portions of the appliance, andthe single lumen mandrel portion subsequently removed from the spunappliance. The appliance may then be placed on or within a framestructure, such as a stent frame. A dip or film coating (such as of FEPor PTFE) may then be applied over the construct to create an imperviousoutside layer and/or to further bond the frame to the spun portion ofthe appliance.

The methods and apparatus disclosed herein may control the thickness ofa tubular structure and thereby the relative permeability of thestructure. As more and more fibers are rotational spun onto a tubularstructure, the tubular structure may both increase in thickness anddecrease in permeability (due to successive layers of strands occludingthe pores and openings of layers below).

Tubular structures produced in connection with the present disclosuremay be described by three general parameters: percent porosity, wallthickness, and fiber diameter. Each of these parameters may impact thenature of the tubular structure, including the tendency of the tubularstructure to permit tissue ingrowth and/or endothelial attachment or thetendency of the tubular structure to resist tissue ingrowth orendothelial attachment. Each of these parameters may be optimized withrespect to each other to create a tubular structure having particularcharacteristics.

Percent porosity refers to the percent of open space to closed space (orspace filled by fibers) in a fiber non-woven material. Thus, the moreopen the non-woven material is, the higher the percent porositymeasurement. In some instances, percent porosity may be determined byfirst obtaining an image, such as using a scanning electron microscope,of a rotational spun material. The image may then be converted to a“binary image,” or an image showing only black and white portions, forexample. The binary image may then be analyzed and the percent porositydetermined by comparing the relative numbers of each type of binarypixel. For example, an image may be converted to a black and white imagewherein black portions represent gaps or holes in the rotational spunmaterial while white portions represent the fibers of the non-wovenmaterial. Percent porosity may then be determined by dividing the numberof black pixels by the number of total pixels in the image. In someinstances, a code or script may be configured to make these analyses andcalculations.

In some embodiments, percent porosities from about 30% to about 80% maybe configured to permit tissue ingrowth into the layer and/or permitendothelial growth or attachment on the layer, including tubularstructures of about 40% to about 60%, tubular structures of about 45% toabout 50%, or tubular structures of about 50% porosity. Less open layersmay be configured to resist such ingrowth and/or attachment. Because thefibers comprising the tubular structures are deposited in successivelayers, the second parameter, wall thickness, may be related toporosity. In other words, the thicker the wall, the more layers offibers and the less porous the wall may be. In some embodiments, a wallwith a thickness from about 20 micrometers to about 100 micrometers maybe configured for use in connection with the present disclosure,including walls from about 40 micrometers to about 80 micrometers.Finally, the third parameter, fiber diameter, may be a measurement ofthe average fiber diameter of a sample in some instances. In someembodiments fiber diameters from about 50 nanometers to about 3micrometers may be used in connection with the present disclosure.Notwithstanding these or other specific ranges included herein, it iswithin the scope of this disclosure to configure a tubular structurewith any combination of values for the given parameters.

In some embodiments the “average pore size” of the tubular structure maybe used as an alternative or additional measurement of the properties ofthe tubular structure. The complex and random microstructure of arotational spun tubular structure presents a challenge to the directmeasurement of the average pore size. Average pore size can beindirectly determined by measuring the permeability of the tubularstructure to fluids using known testing techniques and instruments. Oncethe permeability is determined, that measurement may be used todetermine an “effective” pore size of the rotational spun tubularstructure. As used herein, the “pore size” of a rotational spun tubularstructure refers to the pore size of a membrane which corresponds to thepermeability of the rotational spun tubular structure when measuredusing ASTM standard F316 for the permeability measurement. This standardis described in ASTM publication F316 “Standard Test Methods for PoreSize Characteristics of Membrane Filters by Bubble Point and Mean FlowPore Test,” which is incorporated herein by reference. In some instancesthis test can be used as a quality control after configuring a tubularstructure based on the three parameters (percent porosity, wallthickness, and fiber diameter) discussed above.

In some applications it may be desirable to create a medical appliancewhich is substantially impermeable. Such a layer may decrease theincidence of lumen tissue surrounding the medical appliance growing intoor attaching to the medical appliance. This may be desirable inapplications where the medical appliance is used to treat stenosis orother occlusions; an impermeable outer layer may prevent tissue fromgrowing into or through the material toward or into the lumen of themedical appliance and reblocking or restricting the body lumen. In someembodiments a substantially impermeable outer layer may be produced byusing a rotational spun tubular structure with a percent porosity fromabout 0% to about 50%, including about 25%; a thickness from about 20micrometers to about 100 micrometers, including from about 40micrometers to about 80 micrometers; and fiber diameters from about 50nanometers to about 3 micrometers.

Additionally, or alternatively, a substantially impermeable tubularstructure may have an average pore size of about 0 microns to about 1.5microns. In other embodiments, the impermeable layer may have an averagepore size of less than about 0.5 micron. In yet other embodiments, theimpermeable layer may have an average pore size of less than about 1micron. In some embodiments, the impermeable layer may be a layer otherthan the outer layer, such as a tie layer, an intermediate layer, or aninner layer.

In one example, a medical appliance such as stent or graft may becovered with a rotational spun PTFE inner layer and a rotational spunPTFE outer layer. The outer layer may be configured to be substantiallyimpermeable to tissue ingrowth and/or attachment. In other embodimentsthe impermeability of the stent or graft may be provided by a tie layerdisposed between the outer layer and the inner layer. For example, asubstantially impermeable layer may be formed of FEP which is applied,for example, as a film or dip coating between rotational spun layers ofPTFE. Furthermore, FEP may be rotational spun with a small average poresize to create a substantially impermeable layer. In some embodimentsboth the outer layer and the tie layer may be configured to besubstantially impermeable.

Dip coatings may be applied by dipping a portion of a layer or constructin a polymer dispersion. For example, a PTFE layer may be dip coated ona construct by adding 20 ml of water to 50 ml of a 60 wt % PTFEdispersion to thin the dispersion. A fiber tubular structure may then bedipped in the solution to coat the structure. The dip coat may then besintered at 385 degrees C. for 15 minutes. Other concentrations of PTFEdispersions for dip coatings are also within the scope of thisdisclosure.

Further, an FEP layer may be dip coated on a construct by adding 20 mlof water to 50 ml of a 55 wt % dispersion to thin the dispersion. Afiber tubular structure may then be dipped in the solution to coat thetubular structure. The dip coat may then be cooked, for example, at 325degrees C. for 15 minutes. Other concentrations of FEP dispersions fordip coatings are also within the scope of this disclosure. Additionally,polymer dispersions may be sprayed or otherwise applied onto a surface(such as a fiber tubular structure) to coat the surface. Such coatingsmay be heat treated after application.

In some embodiments, more or less water, for example from about 10 ml toabout 50 ml, may be added to similar amounts and concentrations of thedip dispersions above to thin the dispersions. Additionally, substancesother than, or in addition to, water may be used to thin a dispersionfor dip coating. For example, a surfactant or a solvent may be used. Insome such cases the surfactant or solvent may later be removed from theconstruct, including embodiments where it is allowed to evaporate whenthe coat is sintered or cooked. Alcohols, glycols, ethers, and so forthmay be so utilized.

In some embodiments it may be desirable to create a medical appliancesuch as a stent or graft with an outer layer which is more porous. Aporous outer layer may permit healing and the integration of theprosthesis into the body. For instance, tissue of the surrounding lumenmay grow into the porous outer surface or attach to the outer surfacelayer. This tissue ingrowth may permit, modulate, and/or influencehealing at the therapy site. In some embodiments a porous outer layermay be formed of rotational spun PTFE.

In certain embodiments a relatively porous inner layer may be desirable.This layer may or may not be used in conjunction with a substantiallyimpermeable outer layer. A relatively porous inner layer may permittissue ingrowth and/or endothelial attachment or growth on the insidesurface of the stent or graft which may be desirable for any combinationof the following: healing, biocompatibility, prevention of thrombosis,and/or reduction of turbulent blood flow within the stent or graft. Insome embodiments the inner layer may be comprised of a tubularstructure, such as a rotational spun PTFE tubular structure, having apercent porosity of about 40% to about 80%, including about 50%; athickness of about 20 micrometers to about 100 micrometers, includingfrom about 40 micrometers to about 80 micrometers; and fiber diametersfrom about 50 nanometers to about 3 micrometers.

Lumens within the circulatory system are generally lined with a singlelayer (monolayer) of endothelial cells. This lining of endothelial cellsmakes up the endothelium. The endothelium acts as an interface betweenblood flowing through the lumens of the circulatory system and the innerwalls of the lumens. The endothelium, among other functions, reduces orprevents turbulent blood flow within the lumen. The endothelium plays arole in many aspects of vascular biology, including atherosclerosis,creating a selective barrier around the lumen, blood clotting,inflammation, angiogenesis, vasoconstriction, and vasodilation.

A therapeutic medical appliance which includes a covering of porous orsemi-porous material may permit the formation of an endothelial layeronto the porous surface of the blood contacting side of the medicaldevice. Formation of an endothelial layer on a surface, orendothelialization, may increase the biocompatibility of an implanteddevice. For example, a stent or graft which permits the formation of theendothelium on the inside diameter (blood contacting surface) of thestent or graft may further promote healing at the therapeutic regionand/or have longer-term viability. For example, a stent or graft coatedwith endothelial cells may be more consistent with the surrounding bodylumens, thereby resulting in less turbulent blood flow or a decreasedrisk of thrombosis, or the formation of blood clots. A stent or graftwhich permits the formation of an endothelial layer on the insidesurface of the stent or graft may therefore be particularlybiocompatible, resulting in less trauma at the point of application,fewer side effects, and/or longer-term device viability.

Medical appliances including a covering of porous or semi-porousmaterial may be configured to inhibit or reduce inflammatory responsesby the body toward the tissue contacting side of the medical appliance,for example. Mechanisms such as an inflammatory response by the bodytoward the medical appliance may stimulate, aggravate, or encouragenegative outcomes, such as neointimal hyperplasia. For example, a deviceconfigured to permit tissue ingrowth and/or the growth or attachment ofendothelial cells onto the blood contacting side of the device mayreduce the likelihood of negative flow characteristics and bloodclotting. Similarly, a device so configured may mitigate the body'sinflammatory response toward the material on, for example, the tissue ornon-blood contacting side of the device. By modulating the evokedinflammatory response, negative outcomes such as the presence ofbioactive inflammatory macrophages and foreign body giant cells may bereduced. This may aid in minimizing the chemical chain of responses thatmay encourage fibrous capsule formation surrounding the device andevents stimulating neointimal hyperplasia.

A relatively porous tubular structure may be comprised of a rotationalspun tubular structure, such as PTFE, with an average pore size of about1 micron to about 12 microns, such as from about 2 microns to about 8microns, or from about 3 microns to about 5 microns, or alternativelyfrom about 3.5 microns to about 4.5 microns.

In some embodiments a tie layer may be configured to promote bondingbetween the outer layer and the inner layer. In other embodiments thetie layer may further be configured to provide certain properties to thestent or graft as a whole, such as stiffness or tensile strength. Thetie layer may thus be configured as a reinforcing layer. In someembodiments, expanded PTFE (ePTFE) may be configured as a reinforcinglayer. ePTFE may be anisotropic, meaning having differing properties indiffering directions. For example, ePTFE may tend to resist creep in thedirection the ePTFE membrane was expanded. A reinforcing layer of ePTFEmay be oriented to increase strength, resist creep, or impart otherproperties in a particular direction. ePTFE may be oriented such thatthe expanded direction is aligned with an axial direction of a medicaldevice, with a transverse direction, with a radial direction, at anyangle to any of these directions, and so forth. Similarly, multiplelayers of ePTFE may be disposed to increase strength, resist creep, orimpart other properties in multiple directions. The reinforcing layermay or may not be impermeable.

Additionally, in embodiments where both the inner layer and the outerlayer are porous in nature, the tie layer may be configured to create animpermeable layer between the two porous layers. In such embodiments thestent or graft may permit tissue ingrowth, tissue attachment, and/orhealing on both the inner and outer surfaces of the stent or graft whilestill preventing tissue outside of the stent or graft from growing intothe lumen and occluding the lumen. Thus, tie layers may be configured tocreate a mid-layer portion of a construct, the tie-layer configured toinhibit tissue ingrowth into the layer or to be impervious to tissuemigration into or through the layer, or to substantially inhibit tissuemigration.

Furthermore, the tie layer may be configured to be impervious orsubstantially impervious to fluid migration across the tie layer.Specifically, constructions comprising one or more porous layers mayallow fluid to cross the porous layer. In the case of a medicalappliance configured to control blood flow, such as a graft, a porouslayer may allow blood to leak across the layer or may allow certainsmaller components of the blood to cross the layer while containinglarger components, effectively filtering the blood. In some instancesthis filtration or ultrafiltration may allow components such as plasmato cross the barrier while containing red blood cells, leading toseroma. Thus, a fluid impermeable tie layer may be configured to containfluid within a medical device also comprised of porous layers. In somedevices, a tie layer may be both fluid impermeable and impervious totissue ingrowth, or may be configured with either of these propertiesindependent of the other. Constructs wherein any layer (other than or inaddition to a tie layer) is configured to be fluid impermeable and/orimpervious to tissue ingrowth are also within the scope of thisdisclosure. Thus, disclosure recited herein in connection with fluidimpermeable and/or tissue impervious tie layers may be analogouslyapplied to impermeable layers at various locations within a construct.

The tie layer (or any impermeable/impervious layer) may include anythermoplastic material and may or may not be rotational spun. In oneembodiment, the tie layer may be ePTFE. In another it may be rotationalspun PTFE. In other embodiments it may be FEP, including rotational spunFEP and FEP applied as a film or dip coating. Furthermore, the tie layermay include any of the following polymers or any other thermoplastic:dextran, alginates, chitosan, guar gum compounds, starch,polyvinylpyridine compounds, cellulosic compounds, cellulose ether,hydrolyzed polyacrylamides, polyacrylates, polycarboxylates, polyvinylalcohol, polyethylene oxide, polyethylene glycol, polyethylene imine,polyvinylpyrrolidone, polyacrylic acid, poly(methacrylic acid),poly(itaconic acid), poly(2-hydroxyethyl acrylate),poly(2-(dimethylamino)ethyl methacrylate-co-acrylamide),poly(N-isopropylacrylamide),poly(2-acrylamido-2-methyl-l-propanesulfonic acid),poly(methoxyethylene), poly(vinyl alcohol), poly(vinyl alcohol) 12%acetyl, poly(2,4-dimethyl-6-triazinylethylene),poly(3-morpholinylethylene), poly(N-1,2,4-triazolyethylene), poly(vinylsulfoxide), poly(vinyl amine), poly(N-vinyl pyrrolidone-co-vinylacetate), poly(g-glutamic acid), poly(Npropanoyliminoethylene),poly(4-amino-sulfo-aniline),poly[N-(p-sulphophenyl)amino-3-hydroxymethyl-1,4-phenyleneimino-1,4-phenylene],isopropyl cellulose, hydroxyethyl, hydroxylpropyl cellulose, celluloseacetate, cellulose nitrate, alginic ammonium salts, i-carrageenan,N-[(3′-hydroxy-2′,3′-dicarboxy)ethyl]chitosan, konjac glocomannan,pullulan, xanthan gum, poly(allyammonium chloride), poly(allyammoniumphosphate), poly(diallydimethylammonium chloride),poly(benzyltrimethylammonium chloride),poly(dimethyldodecyl(2-acrylamidoethyly) ammonium bromide),poly(4-N-butylpyridiniumethylene iodine),poly(2-N-methylpridiniummethylene iodine), poly(Nmethylpryidinium-2,5-diylethenylene), polyethylene glycol polymers andcopolymers, cellulose ethyl ether, cellulose ethyl hydroxyethyl ether,cellulose methyl hydroxyethyl ether, poly(1-glycerol methacrylate),poly(2-ethyl-2-oxazoline), poly(2-hydroxyethyl methacrylate/methacrylicacid) 90:10, poly(2-hydroxypropyl methacrylate),poly(2-methacryloxyethyltrimethylammonium bromide),poly(2-vinyl-1-methylpyridinium bromide), poly(2-vinylpyridine N-oxide),poly(2-vinylpyridine), poly(3-chloro-2-hydroxypropyl2-methacryloxyethyldimethylammonium chloride), poly(4-vinylpyridineN-oxide), poly(4-vinylpyridine),poly(acrylamide/2-methacryloxyethyltrimethylammonium bromide) 80:20,poly(acrylamide/acrylic acid), poly(allylamine hydrochloride),poly(butadiene/maleic acid), poly(diallyldimethylammonium chloride),poly(ethyl acrylate/acrylic acid), poly(ethyleneglycol)bis(2-aminoethyl), poly(ethylene glycol)monomethyl ether,poly(ethylene glycol)bisphenol A diglycidyl ether adduct, poly(ethyleneoxide-b-propylene oxide), poly(ethylene/acrylic acid) 92:8, poly(llysinehydrobromide), poly(l-lysine hydrobromide), poly(maleic acid),poly(n-butyl acrylate/2-methacryloxyethyltrimethylammonium bromide),poly(Niso-propylacrylamide),poly(N-vinylpyrrolidone/2-dimethylaminoethyl methacrylate), dimethylsulfatequaternary, poly(N-vinylpyrrolidone/vinyl acetate),poly(oxyethylene)sorbitan monolaurate (Tween 20®), poly(styrenesulfonicacid), poly(vinyl alcohol), N-methyl-4(4′-formylstyryl)pyridinium,methosulfate acetal, poly(vinyl methyl ether), poly(vinylamine)hydrochloride, poly(vinylphosphonic acid), poly(vinylsulfonic acid)sodium salt, and polyaniline.

Regardless of the material, the tie layer may or may not be rotationalspun. Further, in certain embodiments the stent or graft may include twoor more tie layers. The tie layer may be formed in any manner known inthe art and attached to the inner and outer layers in any manner knownin the art. For example, the tie layer may comprise a sheet of materialwhich is wrapped around the inner layer or a tube of material which isslipped over the inner layer which is then heat shrunk or otherwisebonded to the inner and outer layers. Further, in embodiments where thetie layer is rotational spun, it may be rotational spun directly ontothe inner layer, the scaffolding, or both. In some instances the tielayer may be melted after the stent or graft is constructed to bond thetie layer to adjacent layers of the stent or graft covering.

Furthermore, tie layers may be configured to change the overallproperties of the medical appliance. For example, in some instances acover or construct comprised solely of rotational spun PTFE (of thedesired pore size) may not have desired tensile or burst strength. A tielayer comprised of a relatively stronger material may be used toreinforce the PTFE inner layer, the PTFE outer layer, or both. Forexample, in some instances FEP layers may be used to increase thematerial strength of the cover. Again, as discussed above, the tie layermay also be configured as a portion of the construct configured to beimpervious to tissue ingrowth or migration.

Further, one or more layers of rotational spun PTFE may be used inconnection with a scaffolding structure. In other words, the disclosureabove relating to covers, layers, tie layers, and related components isapplicable to any type of scaffolding structure as well as to stents orgrafts with no separate scaffolding structure at all.

In some embodiments, once the inner layer is sintered, the tube ofmaterial may be removed from the mandrel. The inner layer may be“peeled” from the mandrel to initially break any adherence of the innerlayer to the mandrel. The inner layer may also be removed by pushing thecovering with respect to the mandrel, causing the material to bunch asit is removed from the mandrel. In some embodiments, low-frictioncoatings may alternatively or additionally be applied to the mandrelbefore the inner layer is rotational spun. The inner layer may then bereapplied to the mandrel, by slipping the inner layer over the mandrel.

Once the inner layer is reapplied to the mandrel, a wire scaffolding canbe formed over the mandrel and the inner layer. An outer layer ofmaterial may then be rotational spun onto the scaffolding and the innerlayer. The entire construct may then be sintered. Additional layers mayalso be added through similar processes.

Many variations to the above-described process are within the scope ofthe present disclosure. For example, one or more layers may be appliedby wrapping strips or mats of material around the mandrel and/or theother layers. Further, some of the layers may be applied by spray or dipcoating the mandrel and/or the other layers. It is within the scope ofthis disclosure to vary the process above so long as at least one of thelayers is rotational spun using a method and/or system disclosed herein.

In another example, a stent or graft may be comprised of an inner layerof rotational spun PTFE, a tie layer of FEP, and an outer layer of PTFE.The properties of each of these layers, including percent porosity, wallthickness, fiber diameter, and/or average pore size, may be controlledto form a covering layer that inhibits the growth of tissue into orthrough a particular layer or that permits endothelial growth orattachment on a particular layer.

In some such embodiments, the inner layer of PTFE may be spun on amandrel, sintered, removed from the mandrel, replaced on the mandrel,and then a scaffolding structure applied around the inner layer. The FEPtie layer may then be applied by dipping, spraying, applying a filmlayer, electrospinning, rotational spinning, extrusion, or otherprocessing.

In some embodiments, the FEP layer may be heated such that the FEPbecomes soft, in some cases flowing into open spaces in adjacent PTFElayers. This may tie the FEP layer to adjacent PTFE layers. In someinstances, heating the construct to about 325 degrees C. may allow theFEP to partially flow into openings in adjacent PTFE layers, without theFEP completely flowing through the PTFE layer.

In another particular example, an inner layer of PTFE may be rotationalspun on a mandrel, sintered, removed, reapplied, and then a scaffoldingstructure applied around the inner layer. An FEP tie layer may then beapplied as a film layer. In some instances this tie layer may be“tacked” into place, for example, by a soldering iron. A tube of PTFE(which may be formed separately by rotational spinning onto a mandreland sintering) may then be disposed over the FEP film layer. The entireconstruct may then be pressured, for example, by applying a compressionwrap. In some embodiments this wrap may comprise any suitable material,including a PTFE-based material. In other embodiments a Kapton film maybe wrapped around the construct before the compression wrap, to preventthe construct from adhering to the compression wrap.

The compressed layers may then be heated above the melting temperatureof the FEP tie layer, but below the sintering temperature of the PTFE.For example, the melt temperature of the FEP may be from about 264degrees C. to about 380 degrees C., including about 325 degrees C. PTFEmay be sintered at temperatures from about 360 degrees C. to about 400degrees C. Thus, the entire construct may be heated to an appropriatetemperature such as about 325 degrees C. In some embodiments theconstruct may be held at this temperature for about 15 to about 20minutes. Heating the FEP layer to about 325 degrees C. may allow the FEPlayer to remain substantially impervious to tissue ingrowth and/orattachment, creating a “barrier” layer within the construct, while stilladhering the FEP to adjacent layers of PTFE. In other embodiments,heating the construct to higher temperatures, such as about 350 degreesC. or more, may be configured to allow the FEP to flow around the PTFEsuch that the entire construct has a higher degree of porosity and theFEP layer is not as impervious to ingrowth.

The joining of the FEP tie layer to the PTFE outer and inner coverlayers may increase the strength of the finished covering. The constructmay then be cooled and the compression wrap and the Kapton filmdiscarded. The construct may then be removed from the mandrel.

A stent or graft formed by the exemplary process described above may beconfigured with desired characteristics of porosity and strength. Insome instances the FEP material may coat the PTFE nanofibers but stillallow for sufficient porosity to permit tissue ingrowth and/orendothelial attachment or growth. The degree to which the FEP coats thePTFE may be controlled by the temperature and time of processing. Thelower the temperature and/or the shorter the time the construct is heldat temperature, the less the FEP may flow. In some instances a tie layerof FEP which is impervious to tissue ingrowth into or through the layermay be formed by heating the construction only to about 270 degrees C.

A stent or graft may include a cuff at one or both ends of the stent orgraft. The cuff may comprise an additional covering layer on the outsidediameter of the stent or graft, disposed adjacent to the end of thestent or graft. The cuff may be configured to promote tissue ingrowth,attachment, and/or incorporation into the cuff. For example, the cuffmay be more porous than an outer layer of the covering of the stent orgraft. Factors such as porosity, type of covering or coating, type ofmaterial, use of organic material, and/or use or composite materialsformed of synthetic material and organic material may be used to createa cuff configured for tissue ingrowth. Again, the cuff may be configuredto promote tissue ingrowth and/or the growth or attachment ofendothelial cells at one or both ends of the stent or graft. Whenimplanted in the body, the cuffs may tend to “anchor” the ends of thestent or graft with respect to the vessel walls, reducing the relativemovement of the stent or graft ends with respect to the vessel walls.Such a reduction in movement may lessen irritation of the vessel by thestent or graft ends, minimizing complications such as stenosis. Cuffsmay be configured for use in central venous occlusion-type applicationsin some instances. Furthermore, a band of porous material analogous to astent or graft cuff may be coupled to any medical appliance to anchor aportion of such a device.

In some embodiments, the outer layer of the covering of the stent orgraft may be relatively non-porous to inhibit tissue ingrowth into orthrough the outer layer, but the cuff, disposed about the outer layer,may provide a section near each end at which some tissue ingrowth,attachment, and/or incorporation may occur.

The cuff may be comprised of a rotational spun material, such as PTFE,and may be bonded to the outer covering layer through any method,including methods of multilayer device construction described herein.For example, a layer of FEP may be disposed between the outer coveringlayer and the cuff and heated to bond the layers. In other embodimentsthe cuff may comprise a collagen layer which is coupled to the stent orgraft. Further, a co-rotational spun collagen and PTFE cuff may beutilized.

In some embodiments, the medical appliances, including stents andgrafts, may comprise a frame structure provided in connection with oneor more coverings or coatings. It will be appreciated that, thoughparticular structures, coverings, and coatings are described herein, anyfeature of the frames or coverings and/or coatings described herein maybe combined with any other disclosed feature without departing from thescope of the current disclosure.

Frames for use in connection with medical appliances may be fabricatedor formed into particular geometries through a variety of means. Forexample, a frame may be cut from a single tube of material, includingembodiments wherein the frame is first laser cut, then expanded. Inother embodiments, the frame may be molded, including embodimentswherein the frame is molded from a polymeric material. In still otherembodiments, powder metallurgical processes, such as powderedcompression molding or direct metal laser sintering, may be used.

The frame may consist of a single continuous wire. The wire may beshaped in a wave-type configuration. The frame may further be coupled toa covering layer. Additionally, in some embodiments, any covering asdisclosed herein may be applied to any type of frame, for example, lasercut frames, polymeric frames, wire frames, and so forth.

The frame may be designed such that the midsection is “harder” than theends. The “hardness” of the frame refers to the relative strength of thestructure (e.g., its compressibility). A harder portion of the framewill have greater strength (i.e., exert a greater radial outward force)than a softer portion. In one embodiment, the midsection is harder thanthe proximal and distal end sections which are relatively softer.Further, a frame may be configured to be flexible to facilitate theability of the device to conform to the native anatomy at which thedevice is configured for use. Similarly, covered devices may beconfigured with covers which conform to the native anatomy at a therapysite.

Additionally, the frame may be configured to allow the entire device tobe crimped into a relatively low-profile configuration for delivery. Forexample, devices of a certain diameter or constrained profile are morefeasible for delivery at certain vascular or other access points thanothers. For example, in many instances a device configured for insertionvia the radial artery may be relatively smaller than devices configuredfor insertion via the generally larger femoral artery. A frame may beconfigured to be crimped into a particular profile to enable potentialaccess at various or desired access points. Similarly, devices having noframe may be configured to be disposed in a particular profile tofacilitate access and delivery. Once a device is positioned within thebody it may be expanded or deployed in a number of ways, including useof self-expanding materials and configurations. Additionally, someconfigurations may be designed for expansion by a secondary device, suchas a balloon.

The overall frame design may be configured to optimize desired radialforce, crush profile, and strain profile. Methods of designing framesare known in the art and are also disclosed in U.S. patent applicationSer. No. 13/742,025, filed Jan. 15, 2013, the contents of which areincorporated herein in their entirety.

Furthermore, in some embodiments the frame may be configured withradiopaque markers at one or more points along the frame. Such markersmay be crimped to the frame. In other embodiments a radiopaque ribbon,for example a gold ribbon, may be threaded or applied to the frame. Insome embodiments these markers may be located at or adjacent to one orboth ends of the frame. Any radiopaque material may be used, for examplegold or tantalum. Radiopaque elements may be configured to facilitatethe delivery and placement of a device and/or to facilitate viewing ofthe device under fluoroscopy.

In some embodiments, a stent, graft, or other tubular device maycomprise a tapered segment along the length of the device. A taper maybe configured to reduce the velocity of fluid flow within the device asthe fluid transitions from a smaller diameter portion of the device to alarger diameter portion of the device. Reducing the fluid velocity maybe configured to promote laminar flow, including instances wherein atubular member is tapered to promote laminar flow at the downstream endof the device.

Use of rotational spun coatings may facilitate application of a coveringof uniform thickness along a tapered stent or graft. For example, insome embodiments, rotational spun coatings may be configured to evenlycoat devices comprised of various geometries. A rotational spun coatingmay deposit a substantially even coating along various geometries suchas tapers, shoulders, and so forth.

While specific embodiments of stents, grafts, and other medicalappliances have been illustrated and described, it is to be understoodthat the disclosure provided is not limited to the precise configurationand components disclosed. Various modifications, changes, and variationsapparent to those of skill in the art having the benefit of thisdisclosure may be made in the arrangement, operation, and details of themethods and systems disclosed, with the aid of the present disclosure.

Without further elaboration, it is believed that one skilled in the artcan use the preceding description to utilize the present disclosure toits fullest extent. The examples and embodiments disclosed herein are tobe construed as merely illustrative and exemplary and not as alimitation of the scope of the present disclosure in any way. It will beapparent to those having skill in the art, and having the benefit ofthis disclosure, that changes may be made to the details of theabove-described embodiments without departing from the underlyingprinciples of the disclosure herein.

The invention claimed is:
 1. An apparatus for making a rotational spunappliance, the apparatus comprising: a spinneret configured to rotatearound a first axis of rotation and produce spinning fibers; a surfaceconfigured to rotate around the first axis of rotation independentlyfrom rotation of the spinneret; actuators mounted on the rotatablesurface; and mandrels operably connected to the actuators and configuredfor rotation by the actuators, wherein each of the actuators isconfigured to rotate at least one mandrel around its own axis ofrotation, such that each mandrel's own axis of rotation is not the sameas the first axis of rotation; wherein the actuators are configured toselectively rotate the mandrels in a forward direction or a reversedirection relative to the actuators.
 2. The apparatus of claim 1,further comprising a support member configured to rotatably engage andsupport a distal end of each of the mandrels.
 3. The apparatus of claim1, wherein a proximal end of each mandrel is cantilevered by anactuator.
 4. The apparatus of claim 1, wherein the longitudinal axis ofeach of the mandrels is parallel to the surface.
 5. The apparatus ofclaim 4, wherein the longitudinal axis of each of the mandrels extendsradially from the center of the surface, such that each mandrel's axisof rotation is radially different from each other.
 6. The apparatus ofclaim 4, wherein the longitudinal axis of each of the mandrels isoriented perpendicular to the center of the surface, such that eachmandrel's axis of rotation is radially tangential to the first axis ofrotation.
 7. The apparatus of claim 4, wherein the actuators areconfigured to be pivotable to allow the mandrels to either extendradially from the center of the surface or to be oriented perpendicularto the center of the surface.
 8. The apparatus of claim 1, wherein thesurface is configured to be separable from the spinneret and configuredfor placement in a sintering oven.
 9. The apparatus of claim 1, whereinthe mandrels are configured to be separable from the actuators andconfigured for placement in a sintering oven.
 10. The apparatus of claim1, wherein the surface is a disk.
 11. The apparatus of claim 1, furthercomprising a moveable slide configured to allow the rotatable surface tobe moved away from the spinneret during startup and shutdown of thespinneret.
 12. The apparatus of claim 11, wherein the moveable slide isconfigured to allow the rotatable surface and/or mandrels to eitherstartup or slow down rotation while moved away from the spinneret. 13.An apparatus for making a rotational spun appliance, the apparatuscomprising: a hub configured to rotate around a first axis of rotation;a mandrel operably connected to the hub and configured for rotation bythe hub around its own axis of rotation that it is not the same as thefirst axis of rotation, such that during operation of the apparatus, themandrel is rotated around both the first axis of rotation and its ownaxis of rotation; and a spinneret separate from the hub and configuredto also rotate around the first axis of rotation and produce spinningfibers; and a housing configured to allow the hub to be rolled insidethe housing during operation of the apparatus and configured to allowthe hub to be rolled outside the housing when the apparatus is not inoperation.
 14. The apparatus of claim 13, wherein the spinneret ismounted and located in an upper portion of the housing such that thespinneret is located above the hub when the hub is rolled inside thehousing.
 15. The apparatus of claim 13, wherein the housing furthercomprises a retractable cover configured for insertion between thespinneret and the hub, wherein the retractable cover is configured forinsertion between the spinneret and the hub during startup and shutdownof the apparatus.
 16. The apparatus of claim 13, further comprising aplurality of mandrels operably connected to the hub and each configuredfor rotation by the hub around its own axis of rotation, such that eachmandrel's own axis of rotation is not the same as the first axis ofrotation.
 17. The apparatus of claim 16, wherein each of the pluralityof mandrels' own axes of rotation lie in the same plane as each other.18. The apparatus of claim 13, wherein the mandrel is configured to beremovable from the hub.
 19. An apparatus for making a rotational spunappliance, the apparatus comprising: a spinneret configured to rotatearound a first axis of rotation and produce spinning fibers; a surfaceconfigured to rotate around the first axis of rotation independentlyfrom rotation of the spinneret; actuators mounted on the rotatablesurface; and mandrels operably connected to the actuators and configuredfor rotation by the actuators, wherein each of the actuators isconfigured to rotate at least one mandrel around its own axis ofrotation, such that each mandrel's own axis of rotation is not the sameas the first axis of rotation; further comprising a moveable slideconfigured to allow the rotatable surface to be moved away from thespinneret during startup and shutdown of the spinneret.
 20. Theapparatus of claim 19, wherein the moveable slide is configured to allowthe rotatable surface and/or mandrels to either startup or slow downrotation while moved away from the spinneret.